The present invention relates to switching apparatus and, more particularly, to load break air switch apparatus for use in applications such as in terminating and sectionalizing electrical power distribution.
Although load break switch technology is well-developed, there is a constant need for improvement in the areas of operator safety, arc supression, cost-to-rating ratios, versatility of use and compactness.
In certain prior art systems the switchgear is housed within an oil filled tank. The oil afforded a more compact arrangement due to the increased dielectric strength of oil, as compared to air, thereby facilitating arc extinguishing. One such oil filled, load break switch is disclosed in U.S. Pat. No. 4,061,896. There are obvious drawbacks to oil filled switchgear apparatus and, as a result, the switchgear industry has attempted to overcome the design problems caused by arcing without resort to control of the ambient atmosphere surrounding the operating components of the switchgear. In recent years, numerous arc suppression techniques have been employed with varying degrees of success. One such system employs a piston-type arrangement for generating a blast of air to suppress the arc during contact disengagement. While such an arc interruptor arrangement has been found to be effective, its use introduces a number of design problems.
In respect to safety it is imperative that engagement and disengagement of the switch contacts be controlled independently of the action of the human operator (for the reasons discussed in the above-noted U.S. Pat. No. 4,061,896). To this end, so-called "quick make and break" mechanical operators have been developed. These mechanical operators incorporate energy storing systems (such as compression springs) responsive to the action of the human operator to store sufficient energy to cause contact engagement and disengagement at the proper speed regardless of the action of human operator. While the mechanical operator disclosed in U.S. Pat. No. 4,061,896 is capable of effective operation with the oil switch shown in that patent, the utilization of a blow-out type arc suppression device introduces additional mechanical power demands on the operator mechanism which can not be practically satisfied thereby, especially for multi-pole gang operated air switches.
Swtichgear of the type here involved typically incorporate movable contact blades requiring a pivot connection. Proper electrical current flow through the pivot is of course critical and heretofore such has provided problems of current transfer from the pivot rotating member to the pivot stationary member.